Field of the Invention
The present invention relates to a spatial image projection apparatus, and more particularly to a spatial image projection apparatus which projects a spatial image via a projection unit.
Discussion of the Related Art
In general, a spatial image expresses depth, unlike a two-dimensional (2D) planar image. Further, when both eyes of a person perceive a spatial image, the person can experience a three-dimensional (3D) feeling. In addition, a spatial image projection apparatus is configured to project a spatial image, thus making a person experience a 3D feeling as though the person were viewing an actual scene.
Although 3D display technologies using, for example, a polarization, shutter glass, parallax barrier, and lenticular methods have been applied for spatial image projection, these methods require that special glasses be worn in order to view a stereoscopic image, and suffer from a limited view angle when no glasses are used. In addition, another method for spatial image projection is a volumetric method using a rotating screen. Although the volumetric method enables a person to view a 3D image in all directions, the person cannot touch the image because the image is present on a screen.
Another method is a spatial projection display method using a concave mirror or a convex lens. In particular, FIG. 1 is a view illustrating a related art spatial image projection apparatus using a convex lens. As illustrated in FIG. 1, the related art spatial image projection apparatus includes a display panel 10 which displays an image and a convex lens 20 which is spaced apart from the display panel 10 by a given distance and projects an image, which has been displayed on the display panel 10, onto a prescribed space.
Here, a spatial image 30 in the prescribed space is produced at a position forwardly spaced apart from the convex lens 20 by a given distance. In order to produce the spatial image 30 in the prescribed space as described above, a given space is required between the display panel 10 and the convex lens 20. That is, when the distance between the display panel 10 and the convex lens 20 is “da”, the focal distance of the convex lens 20 is “df”, and the distance between the convex lens 20 and the spatial image 30 is “db”, the relationship of 1/db=1/df−1/da is established.
Accordingly, because of the necessity for the given space between the display panel 10 and the convex lens 20 in order to produce the spatial image 30 in front of the convex lens 20, the related art spatial image projection apparatus inevitably requires a very bulky configuration and is of limited usefulness in various fields. In addition, the size of the spatial image 30 is smaller than an image displayed on the display panel 10 because the image on the display panel 10 is projected in front of the convex lens 20.